Early development of Rhizobium-induced root nodules of Parasponia rigida. II. Nodule morphogenesis and symbiotic development

1985 ◽  
Vol 63 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Susan A. Lancelle ◽  
John G. Torrey
Keyword(s):  
Apical Meristem ◽  
Root Nodules ◽  
Lateral Roots ◽  
Infected Tissue ◽  
Host Cells ◽  
Outer Cortex ◽  
Infection Threads ◽  
Thread Formation ◽  
Mature Nodule ◽  
Inner Cortex

The Rhizobium-induced root nodules of Parasponia rigida (Ulmaceae) outwardly resemble those formed on actinorhizal plants, being coralloid in shape and consisting of multiple, branched lobes. The details of nodule morphogenesis also resemble more closely those which occur in an actinorhizal association than a typical Rhizobium–legume association and include prenodule formation, initiation of modified lateral roots which are termed nodule lobe primordia, and rhizobial colonization of tissues derived from the nodule lobe primordia to form the primary nodule lobes. Mature nodule lobe structure is actinorhizallike. Each lobe has an apical meristem and a central vascular cylinder which is surrounded by an uninfected inner cortex and then a zone of infected tissue. Peripheral to the infected tissue is an uninfected outer cortex. Infection threads and intercellular rhizobia progress continuously toward the apical meristem but do not infect the meristem itself. The establishment of the symbiosis in the host cells involves continuous thread formation after the initial infection until the host cells are nearly filled with rhizobia enclosed in threads. The rhizobia remain in threads throughout the symbiotic relationship and are not released from the threads as occurs in bacteroid formation in legumes.

Histological studies of ectomycorrhizae and root nodules from Cercocarpus montanus and Cercocarpus paucidentatus

1971 ◽  
Vol 49 (8) ◽  
pp. 1315-1318 ◽  
Author(s):  
R. E. Hoeppel ◽  
A. G. Wollum II
Keyword(s):  
Host Plant ◽  
Developmental Stages ◽  
Root Nodules ◽  
Lateral Roots ◽  
Growth Chamber ◽  
Cortical Tissue ◽  
Histological Studies ◽  
Histological Sections ◽  
Mature Nodule ◽  
In Cells

The ectomycorrhizae of Cercocarpus montanus Raf. and Cercocarpus paucidentatus Britt. displayed morphologies ranging from single swollen short lateral roots on long roots to terminal pyramidal clusters. Most short roots appeared to be mycorrhizal, although C. paucidentatus was only infected under growth chamber conditions. Histological sections revealed a conspicuous fungal mantle, averaging 30 μ in thickness, and a Hartig's net.The root nodules appeared as swellings on lateral roots, and later formed compact coralloid orange-colored masses several centimeters in diameter. Histological analyses indicated that both species of Cercocarpus harbored a similar endophyte. Three developmental stages were noted in cortical tissue, including (a) hyphal masses in apical nodule cells; (b) hyphae terminating in 3 × 4 μ club-shaped vesicular swellings; and (c) older structureless hyphal masses in cells of mature nodule branches. The older hyphal masses did not appear to be absorbed by the host plant. The endophyte possessed branching filaments 0.5 μ in diameter and was considered to be an actinomycete.

scholarly journals Identification of a Family of Extensin-Like Glycoproteins in the Lumen of Rhizobium-Induced Infection Threads in Pea Root Nodules

2002 ◽  
Vol 15 (4) ◽  
pp. 350-359 ◽  
Author(s):  
Elizabeth A. Rathbun ◽  
Michael J. Naldrett ◽  
Nicholas J. Brewin
Keyword(s):  
Posttranscriptional Regulation ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Regulation Of Gene Expression ◽  
Pcr Primers ◽  
Amino Acid Sequences ◽  
Sequence Conservation ◽  
Host Cells ◽  
Cdna Clones ◽  
Infection Threads

Rhizobium leguminosarum bv. viciae normally gains access to pea host cells through tubular cell wall ingrowths termed infection threads. Matrix glycoprotein (MGP), a major component of the infection thread lumen, is also secreted from the tips of uninoculated roots and can be released into solution under reducing conditions. Monoclonal antibody MAC265, which recognizes MGP through a carbohydrate epitope, was used for immunoaffinity purification of the glycoprotein from pea roots. Following treatment with chymotrypsin, a peptide fragment was obtained and subjected to N-terminal sequencing. Using PCR primers based on this sequence, cDNA clones were isolated with RNA from inoculated roots and nodules. DNA sequencing of 30 of these clones revealed a family of closely related and repetitive polypeptides with (hydroxy)proline-rich motifs. The cDNA sequences showed over 70% identity with the deduced amino acid sequences of plant extensins, particularly with VfNDS-E from Vicia faba and MtN12 from Medicago truncatula, both of which are strongly upregulated in legume root nodules. Root nodule extensins from pea were of variable length but showed strong sequence conservation of the N-terminus, of the C-terminus, and of a central domain comprising 33 amino acids that were sometimes reiterated. The distribution of tyrosine residues suggested the possible importance of intramolecular and intermolecular cross-linking. There was strong sequence conservation with MtN12 in the 3′-untranslated region, suggesting a possible involvement in posttranscriptional regulation of gene expression.

scholarly journals Morphology of root nodules and nodule-like structures formed by Rhizobium and Agrobacterium strains containing a Rhizobium meliloti megaplasmid.

1983 ◽  
Vol 97 (3) ◽  
pp. 787-794 ◽  
Author(s):  
C H Wong ◽  
C E Pankhurst ◽  
A Kondorosi ◽  
W J Broughton
Keyword(s):  
Normal Development ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Root Hairs ◽  
Host Cells ◽  
Donor Strain ◽  
Intercellular Spaces ◽  
Infection Threads ◽  
Infected Cells ◽  
Rhizobium Sp

We examined expression of the megaplasmid pRme41b of Rhizobium meliloti in two different Rhizobium sp. Strains and in Agrobacterium tumefaciens. Transfer of pRme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of RP4 into the nif region (Kondorosi, A., E. Kondorosi, C.E. Pankhurst, W. J. Broughton, and Z. Banfalvi, 1982, Mol. Gen. Genet., 188:433-439). In all cases, transconjugants formed nodule-like structures on the roots of Medicago sativa. These structures were largely composed of meristematic cells but they were not invaded by bacteria. Bacteria were found only within infection threads in root hairs, and within intercellular spaces of the outermost cells of the structures. The donor strain of R. meliloti containing pAK11 or pAK12 in pRme41b initially produced nodules on M. sativa that did not fix nitrogen (Fix-). In these nodules, bacteria were released from infection threads into the host cells but they did not multiply appreciably. Any bacteroids formed degenerated prematurely. In some cases, however, reversion to a Fix+ phenotype occurred after 4 to 6 wk. Bacteria released into newly infected cells in these nodules showed normal development into bacteriods.

scholarly journals The structure and physiological significance of the root-nodules of Myrica gale

1911 ◽  
Vol 84 (571) ◽  
pp. 215-216 ◽  
Keyword(s):  
Apical Meristem ◽  
Root Nodules ◽  
Lateral Roots ◽  
Physiological Significance ◽  
Cultivated Plants ◽  
Myrica Gale ◽  
The North

The peculiar nodule formations on the roots of Myrica gale were first described and figured by Brunchorst in 1886, who stated that they were caused by an inhibiting fungus with septate hyphæ and terminal spores. Möller in 1890 placed this fungus in the group Frankia, naming it Frankia Brunchorstii , and considered it to be closely related to a similar fungus in Alder nodules. In 1902 Shibara stated that the fungus is found exclusively in a peripheral sub-cork layer of tissue, one to three cells thick, and because of its peculiar ray-branching and club-shaped spores, it belongs to the group Actinomyces. Peklo in 1910, working on greenhouse-grown plants, supported Shibata’s view. Roots of Myrica gale were obtained for this investigation from plants growing wild in Wales, Ireland, and the North of England, and from cultivated plants growing in the Chelsea Physic Gardens. In all cases the roots were found to possess nodules of varying size. The young nodules are from 2-3 mm. long and 0·8-1 mm. broad, but these by branching form “clusters,” sometimes as large as a nutmeg, and surrounded by peculiar rootlets which grow out through the end of each nodule or branch. The branching is associated with the outgrowth of lateral roots, and is not due to dichotomy of the apical meristem of the root as is the case in the nodules of Cycas, Alder, and Elæagnus.

scholarly journals Cell Biological Changes of Outer Cortical Root Cells in Early Determinate Nodulation

2001 ◽  
Vol 14 (7) ◽  
pp. 839-847 ◽  
Author(s):  
Paulina C. van Spronsen ◽  
Mette Grønlund ◽  
Cristina Pacios Bras ◽  
Herman P. Spaink ◽  
Jan W. Kijne
Keyword(s):  
Lotus Japonicus ◽  
Nod Factors ◽  
Outer Cortex ◽  
Root Cortex ◽  
Root Cells ◽  
Leguminous Plants ◽  
Infection Threads ◽  
Cytoplasmic Bridges ◽  
Inner Cortex

In the symbiosis of leguminous plants and Rhizobium bacteria, nodule primordia develop in the root cortex. This can be either in the inner cortex (indeterminate-type of nodulation) or outer cortex (determinate-type of nodulation), depending upon the host plant. We studied and compared early nodulation stages in common bean (Phaseolus vulgaris) and Lotus japonicus, both known as determinate-type nodulation plants. Special attention was paid to the occurrence of cytoplasmic bridges, the influence of rhizobial Nod factors (lipochitin oligosaccharides [LCOs]) on this phenomenon, and sensitivity of the nodulation process to ethylene. Our results show that i) both plant species form initially broad, matrix-rich infection threads; ii) cytoplasmic bridges occur in L. japonicus but not in bean; iii) formation of these bridges is induced by rhizobial LCOs; iv) formation of primordia starts in L. japonicus in the middle root cortex and in bean in the outer root cortex; and v) in the presence of the ethylenebiosynthesis inhibitor aminoethoxyvinylglycine (AVG), nodulation of L. japonicus is stimulated when the roots are grown in the light, which is consistent with the role of cytoplasmic bridges during nodulation of L. japonicus.

scholarly journals Ultrastructural and Cytochemical Investigation of Asymptomatic Infection by Pythium spp.

1998 ◽  
Vol 88 (3) ◽  
pp. 234-244 ◽  
Author(s):  
Patrice Rey ◽  
Nicole Benhamou ◽  
Yves Tirilly
Keyword(s):  
Asymptomatic Infection ◽  
Infection Process ◽  
Host Cells ◽  
Striking Difference ◽  
Outer Cortex ◽  
Root Cells ◽  
Defense Reactions ◽  
Cytochemical Investigation ◽  
A Minor ◽  
Inner Cortex

The influence exerted by Pythium group F (a minor pathogen ubiquitous in soilless cultures) and P. uncinulatum (a nonpathogenic species) colonization on tomato roots was investigated. In both interactions, infected roots did not exhibit obvious symptoms; however, major physiological changes occurred within the host tissues colonized by Pythium group F compared to P. uncinulatum. According to our cytological observations, Pythium group F colonization involved a series of events: first, development and growth of the fungus in the epidermis and outer cortex tissues, which was associated with marked host cell disorganization and even breakdown. In colonized roots, symptoms were not easily discernible because alterations were restricted to the epidermis and outer cortex tissues. Second, pathogen ingress in the inner cortex and stele tissues was associated with massive induction of host defense reactions and alteration of invading hyphae. In a complex interaction that involved major metabolic changes in root cells, an array of defense-related reactions was produced, as exemplified by the formation of wall appositions and plugging of host cells with osmiophilic, electron-dense, granular, or fibrillar materials. P. uncinulatum growth was restricted to the epidermis and outer cortex tissues and associated with relatively minor damage to host cells. P. uncinulatum colonization of root tissues did not result in defense events similar to those observed in Pythium group F-infected inner cortex and stele tissues. Moreover, most of the invading P. uncinulatum hyphae were moribund. The results of the current study indicated that symptomless infections can be insignificant in terms of pathology for the plant (i.e., P. uncinulatum) or can be potentially dangerous (i.e., Pythium group F). Our results clearly showed a striking difference between nonpathogenic and minor pathogenic Pythium spp. attacks. The description of the Pythium group F infection process suggests that this interaction is unique, because the fungus behaves as a necrotrophic fungus in the epidermis and outer cortex tissues, whereas it is a potential inducer of plant defense reactions in the inner cortex and stele tissues. To our knowledge, cytological events similar to those observed with Pythium group F have not been described until now, even though descriptions of these events could help elucidate several aspects of the relationships between plants and minor pathogens.

A light and electron microscope study of the fungal endophytes in the sporophyte and gametophyte of Lycopodium cernuum with observations on the gametophyte–sporophyte junction

1992 ◽  
Vol 70 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Jeffrey G. Duckett ◽  
Roberto Ligrone
Keyword(s):  
Root Nodules ◽  
Fungal Endophytes ◽  
Fungal Endophyte ◽  
Peninsular Malaysia ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Material ◽  
Intercellular Spaces ◽  
Host Cytoplasm ◽  
Fungal Associations

The ventral epidermal cells of the photosynthetic, surface-living gametophytes of Lycopodium cernuum, collected from moist shaded banks in Peninsular Malaysia, contain an aseptate fungus. In some cells the hyphae are thick walled and form coils encapsulated by a thin layer of host wall material. In others the fungus is thin walled and shows limited differentiation into larger trunk hyphae and arbuscules. The adjacent host cytoplasm, separated from the fungus by a granular interfacial matrix, contains numerous chloroplasts, mitochondria, and microtubules. The hyphae contact the substratum via the ventral walls of the epidermal cells and the rhizoids are free from infection. In the protocorm and root nodules, aseptate hyphae initially colonize mucilage-filled schizogenous intercellular spaces. Subsequent invasion of the host cells is associated with the development of massive overgrowths of host wall material. The fungal associations in L. cernuum share a mixture of attributes otherwise found in different angiosperm mycorrhizae and in mycotrophic relationships in liverworts. Wall ingrowths are present in both the gametophyte and sporophyte cells in the placenta of L. cernuum. The very limited development of the placenta, compared with L. appressum, certain bryophytes and ferns, the diminutive size, and early senescence of the gametophytes of L. cernuum are all linked to the presence of the protocorm. This massive absorptive organ, homologous to a foot, in terms of its position in sporophyte ontogeny, but external to the parent gametophyte, derives its nutrition partly from photosynthesis and partly from its fungal endophyte. Key words: chloroplasts, Lycopodium, mycorrhiza, pteridophytes, root nodules, symbiosis, transfer cells.

scholarly journals Identification of Symbiotically Defective Mutants of Lotus japonicus Affected in Infection Thread Growth

2006 ◽  
Vol 19 (12) ◽  
pp. 1444-1450 ◽  
Author(s):  
Fabien Lombardo ◽  
Anne B. Heckmann ◽  
Hiroki Miwa ◽  
Jillian A. Perry ◽  
Koji Yano ◽  
...  
Keyword(s):  
Root Hair ◽  
Plant Cell Wall ◽  
Plant Root ◽  
Lotus Japonicus ◽  
Cortical Cell ◽  
Host Cells ◽  
Infection Thread ◽  
Mycorrhizal Symbiosis ◽  
Symbiotic Interaction ◽  
Infection Threads

During the symbiotic interaction between legumes and rhizobia, the host cell plasma membrane and associated plant cell wall invaginate to form a tunnel-like infection thread, a structure in which bacteria divide to reach the plant root cortex. We isolated four Lotus japonicus mutants that make infection pockets in root hairs but form very few infection threads after inoculation with Mesorhizobium loti. The few infection threads that did initiate in the mutants usually did not progress further than the root hair cell. These infection-thread deficient (itd) mutants were unaffected for early symbiotic responses such as calcium spiking, root hair deformation, and curling, as well as for the induction of cortical cell division and the arbuscular mycorrhizal symbiosis. Complementation tests and genetic mapping indicate that itd2 is allelic to Ljsym7, whereas the itd1, itd3, and itd4 mutations identified novel loci. Bacterial release into host cells did occur occasionally in the itd1, itd2, and itd3 mutants suggesting that some infections may succeed after a long period and that infection of nodule cells could occur normally if the few abnormal infection threads that were formed reached the appropriate nodule cells.

scholarly journals AT-HOOK MOTIF NUCLEAR LOCALISED PROTEIN 18 as a Novel Modulator of Root System Architecture

2020 ◽  
Author(s):  
Marek Šírl ◽  
Tereza Šnajdrová ◽  
Dolores Gutiérrez-Alanís ◽  
Joseph G. Dubrovsky ◽  
Jean Phillipe Vielle-Calzada ◽  
...  
Keyword(s):  
Root System ◽  
System Architecture ◽  
Lateral Root ◽  
Apical Meristem ◽  
Lateral Roots ◽  
Primary Root ◽  
Root System Architecture ◽  
Root Apical Meristem ◽  
Root Initiation ◽  
Lateral Root Initiation

The AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN (AHL) gene family encodes embryophyte-specific nuclear proteins with DNA binding activity. They modulate gene expression and affect various developmental processes in plants. We identify AHL18 (At3G60870) as a developmental modulator of root system architecture and growth. AHL18 regulates the length of the proliferation domain and number of dividing cells in the root apical meristem and thereby, cell production. Both primary root growth and lateral root development respond according to AHL18 transcription level. The ahl18 knock-out plants show reduced root systems due to a shorter primary root and a lower number of lateral roots. This change results from a higher number of arrested and non-developing lateral root primordia (LRP) rather than from decreased initiation. Overexpression of AHL18 results in a more extensive root system, longer primary roots, and increased density of lateral root initiation events. Formation of lateral roots is affected during the initiation of LRP and later development. AHL18 regulate root apical meristem activity, lateral root initiation and emergence, which is in accord with localization of its expression.

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